The purpose of this application is to request support for participation in the scientific and clinical activities of the Pediatric Oncology Group. Our aims are: 1. To develop new hypotheses about the nature and treatment of childhood cancer by innovative laboratory and clinical investigations in this center. 2. To subject hypotheses of apparent merit to testing in cooperative studies with other member institutions of the Pediatric Oncology Group. 3. To collaborate with other institutions in the Group in evaluation of hypotheses generated by them or nonmember institutions. 4. To participate in critical analysis, discussion and interpretation of results of group studies. By coordinated utilization of the multiple clinical and laboratory people and resources available to group institutions accelerated progress toward better control of children's cancer is anticipated.